Detection of putative dopamine receptors in neurites outgrowing from locust central nervous system explants using anti-idiotypic dopamine antibodies

Organotypic cultures established from the third thoracic ganglion of locust embryo have been used to investigate dopamine receptors. In this in vitro system, neurites emerge directly from the explants and form a dense network around the explants, presenting cell surface freely exposed for experimental labelling. Polyclonal anti-idiotypic antibodies raised in rabbits to antibodies against dopamine conjugate, and previously found to bind to dopamine receptors, have been used to investigate putative dopamine receptors in these neurites. Immunocytochemical detection by light microscopy employing immunofluorescence labelling, was correlated with electron microscopy, using peroxidase staining. In addition to a location for dopamine receptors on the neurite surface, intracellular binding sites were also found in neurites. This internal labelling might represent an intracellular pool of dopamine receptor precursors. The labelling was specific in that it was not present when the anti-idiotypic dopamine antibodies were replaced with non-immune serum or when preincubation with conjugated dopamine preceded incubation with anti-idiotypic dopamine antibodies.

Distribution of dopaminergic fibers in the central division of the extended amygdala of the rat

The distribution of dopaminergic fibers in the principal components of the central extended amygdala (central amygdaloid nucleus (Ce), substantia innominata, and bed nucleus of the stria terminalis (BNST)), was studied using immunocytochemistry against tyrosine hydroxylase, dopamine beta-hydroxylase and dopamine. Dopamine fibers were found most densely distributed in the dorsolateral subdivision of the BNST and the lateral part of the Ce. Smaller numbers of dopaminergic fibers were found in the rest of the central extended amygdala. In contrast, dopamine beta-hydroxylase fibers were virtually absent from the dorsolateral bed nucleus of the stria terminalis and lateral part of the central amygdaloid nucleus, but were distributed in a moderate density in the medial part of Ce, dorsal substantia innominata and posterolateral BNST. Our results show that dopamine fibers are most concentration over those regions of the central extended amygdala with large numbers of GABAergic neurons whose projections remain within the central extended amygdala, while noradrenergic fibers are most heavily concentrated over those regions containing a large proportion of brainstem projection neurons. That dopamine fibers are concentrated over regions with GABAergic medium spiny neurons suggests that those regions might be organized as a striatal parallel.

The postnatal maturation of dopamine innervation in the prefrontal cortex of gerbils (Meriones unguiculatus) is sensitive to an early single dose of methamphetamine. A quantitative immunocytochemical study

Dopamine (DA)-immunoreactivity was investigated in the prefrontal cortex (PFC) of 90 day old adult male gerbils (Meriones unguiculatus) after they had received a single dose of either methamphetamine (50 mg/kg; i.p.) or saline at the age of postnatal day 14. For that purpose, a selective and sensitive antibody directed against glutaraldehyde-conjugated dopamine was applied. All detectable fragments of dopamine-immunoreactive fibres were identified in consecutive frontal sections of the pregenual prefrontal cortex, and their total numbers and total length were determined in the medial (mPFC) and orbital prefrontal cortex (oPFC). The results indicate that a single application of methamphetamine during early postnatal development caused a significant and severe restraint of the subsequent maturation of the prefrontal dopamine-innervation. Although, on postnatal day 14, the total dopamine-immunoreactivity had only attained about 4% (mPFC) and 7% (oPFC) of the regular adult values, this solitary pharmacological challenge entailed final adult innervation densities which were about 38% (mPFC) and 50% (oPFC) below those of the controls. Considering the pivotal role which mesoprefrontal dopaminergic afferents play in morphogenesis and regular functioning, the present results are discussed with current understanding of structural and functional plasticity during maturation of the prefrontal cortex.

[The effect of catecholamine and serotonin antibodies on pain sensitivity and the development of morphine tolerance in experimental drug addiction]

The effect of antibodies to catecholamine and serotonin on the thermal pain sensitivity and tolerance to morphine was studied in rats immunized by protein-conjugated neurotransmitters before chronic drug intoxication. The antibodies to catecholamine have been found to affect bifunctionally on the nociception bifunctionally: either accelerating or delaying the pain reaction to thermal irritation. The antibodies to serotonin were ineffective as modulators both of the pain sensitivity and tolerance to morphine development. In contrast, the antibodies to catecholamine suppressed the expression of tolerance to chronic morphine. Serotonin antibodies virtually produced no effects on pain sensitivity and the development of morphine tolerance.

Demonstration of immunoglobulin G with affinity for dopamine in cerebrospinal fluid from psychotic patients

Using an enzyme-linked immunosorbent assay, significantly raised concentrations of immunoglobulin G with affinity for the neurotransmitter dopamine were demonstrated in cerebrospinal fluid from psychotic patients. We have varied the antigen presentation in order to find a conjugate with low unspecific binding. The conjugation of dopamine to carbodiimide-activated poly-L-glutamic acid and that to activated succinimide ester of biotin are described. The use of glutaraldehyde conjugation is not recommended because of the risk of formation of tetrahydroisoquinolines. A strong correlation (r = 0.94, P < 0.001) between the results obtained with dopamine conjugated to poly-L-glutamic acid and dopamine conjugated to biotin was observed. Forty-two human cerebrospinal fluid samples from 20 psychotic patients, (12 with a bipolar disorder and 8 with schizophrenia) and 22 control patients, with various neurological diseases but no apparent psychiatric diseases were investigated. A significantly higher incidence (P < 0.001) of antibodies with affinity for dopamine were found in the group of psychotic patients compared with the neurological control group.

New aspects of dopaminergic interplexiform cell organization in the goldfish retina

Dopaminergic interplexiform cells (DA-IPCs) in the goldfish retina have been reexamined by light and electron microscopic immunocytochemistry with antisera against dopamine (DA) or tyrosine hydroxylase (TH). Successful immunostaining with a specific anti-DA antiserum offers further direct support for DA-IPCs. Anti-DA immunocytochemistry in combination with [3H]-DA autoradiography shows 92% colocalization of the two markers, indicating that [3H]-DA autoradiography is a reliable technique for identification of DA-IPCs. Incubations with anti-TH antiserum show that immunoreactive DA-IPCs have a homogeneous distribution, with an average frequency of 71 +/- 8 cells/mm2 in retinas of 14-15 cm long goldfish. Their arrangement is distinctly nonrandom. Electron microscopy of TH-immunoreactive cell processes confirms that horizontal cell axons synapse onto DA-IPCs and adds the following junctional arrangements to the circuit diagram of the DA-IPC: 1) adjacent serial synapses between DA-IPCs, external horizontal cells, and putative glycinergic interplexiform cells, 2) junctional appositions between DA-IPCs and photoreceptor cells, 3) junctional appositions between neighbouring DA-IPCs, and 4) the "gap junctional complex," typically consisting of a DA-IPC process juxtaposed with a gap junction between horizontal cell axons. The gap junction is flanked by clusters of small, round vesicles and groups of electron-dense structures resembling intermediate filaments. These morphological results support the functional involvement of DA-IPCs in adaptive retinomotor movements and in horizontal cell gap junction modulation and/or dynamics. They also suggest particular interaction between the dopaminergic and the glycinergic IPC system in the outer plexiform layer of goldfish retina.

Identification of L-dopa immunoreactivity in some neurons in the human mesencephalic region: a novel dopa neuron group?

The presence of L-3,4-dihydroxyphenylalanine (L-DOPA) immunoreactivity is reported for the first time in some neurons in the human mesencephalic region, using an immunohistochemical method with a newly raised, highly specific anti-L-DOPA antiserum. We have found many L-DOPA-positive/dopamine (DA)-positive and a few L-DOPA-positive/DA-negative cell bodies in dopaminergic regions in the midbrain. The present results suggest the existence of more than one neuronal group of L-DOPA in the human mesencephalon. L-DOPA in one group is an intermediate metabolite for decarboxylation to DA and in another group may exist as an end-product. L-DOPA in the latter neurons could be a neuromodulator and/or neurotransmitter. Thus, we suggest that L-DOPA plays an important role besides being an intermediate of DA in the human mesencephalon.

Radioimmunoligand characterization and immunohistochemical localization of dopamine D2 receptors on rods in the rat retina

The retinal neurotransmitter dopamine (DA), elaborated from intrinsic dopaminergic neurons as amacrine and interplexiform cells, is known to modulate several complex functions mediated by D1 and D2 receptors in the vertebrate retina. In this paper, we characterized and localized DA receptors of the D2 family on rod outer segments (ROS) of the rat retina by a radioimmunoligand binding assay and by immunohistochemistry. Anti-anti-DA conjugated antibodies (or anti-idiotypic antibodies Ab2) were used as ligand; BSA-glutaraldehyde-conjugated spiperone, eticlopride (D2 antagonists) and DA were used as displacers. The linear Scatchard transformation indicated that data were best fit to the one-site model. By using the peroxidase-antiperoxidase technique, an intense labeling was located on rods. These results supported the paracrine action of DA on the photoreceptor cell.

[The effect of epitope density on the immunogenic properties of hapten-protein conjugates]

The model of T-dependent dopamine-protein conjugates prepared by the glutaraldehyde method was used to study the influence of hapten valence and molecular weight on the immunogenicity of these conjugates. The immunogenicity of dopamine-protein conjugates increased in the range of DA4-BSA--DA5,8-BSA--DA14-BSA and decreased with further increase of hapten density. It was assumed that partial tolerogenic properties of DA18-22-BSA were due to nonspecific mechanisms associated with changes in the physical molecular characteristics of the antigen during the procedure of conjugation, rather than to specific mechanisms. The latter are more typical for low substituted conjugates.

Electroacupuncture accelerated the expression of c-Fos protooncogene in dopaminergic neurons in the ventral tegmental area of the rat

The mesolimbic dopaminergic system has been implicated in mediating morphine and electroacupuncture analgesia. In the present study, Fos immunoreactivity was used as a marker of neuronal activity to investigate if electroacupuncture could activate the dopaminergic neurons in the midbrain. Electroacupuncture stimulation significantly increased the number of Fos-positive dopaminergic neurons in the ventral tegmental area (VTA), whereas no significant c-fos expression in the dopaminergic neurons was observed in the substantia nigra (SN). These results indicate that the VTA rather than the SN may play a role in mediating electroacupuncture analgesia.

Neurochemical alterations but not nerve cell loss in aged rat neostriatum

Numerical changes in the overall neostriatal neuronal population have been investigated by morphometric analysis of Nissl-stained and glucocorticoid receptor-immunoreactive neurons. Number and staining intensity of various chemically-identified nerve cell populations were analysed by means of immunocytochemistry coupled with computer-assisted image analysis. Three- and 24-month-old male Sprague-Dawley rats were used. No change in the number of Nissl-stained, glucocorticoid receptor-, dopamine and adenosine 3':5'-monophosphate-regulated phosphoprotein- and enkephalin-immunoreactive neurons and a 50% decrease of neuropeptide Y-immunoreactive neurons were observed in the aged rat. In our preparations, the glucocorticoid receptor antibody stains around 90% of the neostriatal neurons, the dopamine and adenosine 3':5'-monophosphate-regulated phosphoprotein and enkephalin antibodies label 25-35% and the neuropeptide Y antibody stains only 1% of neostriatal neurons. In the same preparations a significant decrease in the intensity of immunostaining was observed for enkephalin-, dopamine and adenosine 3':5'-monophosphate-regulated phosphoprotein- and neuropeptide Y-immunoreactive neuronal cell bodies and tyrosine hydroxylase-immunoreactive nerve terminals in the aged rat. In the case of neuropeptide Y- and dopamine and adenosine 3':5'-monophosphate-regulated phosphoprotein-immunoreactive neurons, the changes in the intensity of immunostaining were differentially compartmentalized within neostriatum, suggesting selective vulnerability of striatal subregions to ageing processes. In conclusion, these data indicate that no significant age-related neuronal cell loss occurs in neostriatum. On the other hand, a generalized decrease in the levels of peptide transmitters and molecules related to dopamine transmission is observed in aged rat neostriatum, possibly resulting in the known age-related deficits of neostriatally-controlled behaviours.

Characterization of the dopaminergic innervation of the primate frontal cortex using a dopamine-specific antibody

The mesencephalic dopaminergic system has been implicated in the motor and cognitive operations of the cerebral cortex as well as in the pathogenesis of neurological and psychiatric disorders. However, to date, the dopamine (DA)-containing axons of the primate cerebral cortex have not been directly visualized immunohistochemically due to the lack of a DA-specific antibody. We have now analyzed the regional and laminar distribution of DA-immunoreactive (DA-IR) afferents in the frontal cortex of the rhesus monkey using a monoclonal antibody specific for DA. In addition, we compared the distribution of DA-IR processes to tyrosine hydroxylase (the rate-limiting enzyme in DA synthesis) immunoreactive (TH-IR) axons. Frontal cortex displays an elaborate and robust dopaminergic innervation. Although regional differences in the DA-IR innervation were clearly evident, variations in the DA innervation were essentially unrelated to cytoarchitectonic boundaries. Instead, the DA innervation followed two basic gradients: (1) a prominent medial-to-lateral gradient of decreasing fiber density that was most prominent in the dorsal cortical regions, and (2) a more subtle anterior-posterior gradient in which DA-IR fiber density decreased slightly in both rostral and caudal directions from a peak density centered in the region of granular frontal area 8Bm and the supplementary motor area 6M. The laminar pattern of DA-IR axons also showed regional variations that again were typified by smooth transitions irrespective of cytoarchitecture. Analysis of DA-IR axonal morphology indicated that immunoreactive fibers form a basically uniform population, giving little evidence of a bimodal heterogeneity evident in other species.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunolocalization of catecholamine enzymes, serotonin, dopamine and L-dopa in the brain of Dicentrarchus labrax (Teleostei)

Antisera to serotonin (5-HT), dopamine, and L-dopa, and to the catecholamine synthesizing enzymes, tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyl transferase (PNMT), were used to localize monoamine containing neurones in the brain of Dicentrarchus labrax (sea bass). In the brain stem, 5-HT-immunoreactive (ir) neurones were recognized in the ventrolateral medulla, vagal motor area, medullary, and mesencephalic raphe nuclei and in the dorsolateral isthmal tegmentum. In the hypothalamus, liquor-contacting 5-HT neurones were seen in various regions of the paraventricular organ. Virtually all regions of the brain contained a dense innervation by 5-HT fibres and terminals. DBH-ir neurones were restricted to three brain stem areas: the locus coeruleus, the area postrema, and the reticular formation of the lower medulla. Neurones in these three groups also displayed TH-ir, and in the latter area, PNMT-ir in addition. In the locus coeruleus and area postrema, TH-ir neurones outnumbered DBH-ir neurones, an observation substantiated by the presence of dopamine-ir neurones. In the forebrain, dopamine- and TH-ir neurones were found in the olfactory bulb, ventral/central telencephalon, periventricular preoptic, and suprachiasmatic areas, dorsolateral and ventromedial thalamus, and posterior tuberal nucleus. In the paraventricular organ, the distribution and morphology of dopamine-ir neurones was similar to that observed with anti-5-HT, but the vast majority of cells were not TH-ir, suggesting accumulation of dopamine by uptake from the ventricle, rather than by synthesis. L-dopa-ir neurones were found only in the central telencephalon, preoptic recess, and dorsolateral thalamus. Fibres and terminals immunoreactive for dopamine, TH, and DBH showed a broadly similar distribution. The results are discussed in relation to the monoaminergic systems previously reported in other teleostean species and the mammalian brain.

Stimulant-induced alterations in dopaminergic and serotonergic function in fetal raphe neurons

Methamphetamine and its structural analogues have been demonstrated to be neurotoxic to CNS dopamine (DA) and serotonin (5-HT) neurons both in vivo and in vitro. Our laboratory has been actively characterizing mesencephalic cultures and the effects of methamphetamine exposure on neurochemical and immunochemical indices. The purpose of the present studies was to extend our findings with mesencephalic cultures and compare them with methamphetamine-induced alterations in fetal raphe cultures that contain both DA and 5-HT cells. Methamphetamine (10 and 100 microM) was added to the cultures 24 h after plating and fresh daily thereafter. The effects of chronic methamphetamine exposure on [3H]-DA and [3H]-5-HT uptake were determined after 5 days of drug treatment. Additional cultures were immunochemically analyzed for the presence of DA- and 5-HT-containing cells and total neuronal density. Results indicate that repeated methamphetamine exposure decreased DA and 5-HT uptake. Furthermore, repeated exposure to the higher concentration of methamphetamine (100 microM) caused a significant reduction in the number of DA and 5-HT cells as well as reducing the total neuronal density. This would suggest that this higher concentration of methamphetamine results in generalized neurotoxicity. Exposure to 10 microM methamphetamine resulted in more specific effects on dopaminergic function. These findings indicate that repeated methamphetamine administration can induce similar alterations in both dopaminergic and serotonergic neurons in raphe cultures.

Immunohistochemical colocalization of tyrosine hydroxylase and estradiol receptors in the sheep arcuate nucleus

In sheep, the arcuate nucleus contains numerous tyrosine hydroxylase (TH) and estradiol receptor (rE2) immunoreactive (IR) perikarya and it has been shown previously in this species that catecholaminergic neurons can mediate the gonadal steroid action on the reproductive function. In the present study, double immunohistochemical labelling with antibodies against TH and rE2 have been used to demonstrate the presence of rE2 in TH-IR neurons in the arcuate nucleus where the distribution of TH-IR and rE2-IR neurons overlap each other. Only less than 10% of all the rE2-IR perikarya presented TH immunoreactivity. It was therefore hypothesized that either such a low number of double labelled neurons can support the effects of estradiol in this area or that the effect of this steroid was indirect. In the latter case it might be first mediated by beta-endorphin neurons which have been previously described in this nucleus.

Participation of a GABA-ergic system in the processes of neuroimmunomodulation

Participation of a GABA-ergic system in neuroimmunomodulation was established through the use of a large number of chemical compounds which selectively modulate the activity of the GABA-BD-receptor-ionophore complex. Activation of the GABA-receptors with muscimol or activation of the BD-receptors with diazepam or tazepam had stimulatory effects upon immunogenesis. A decrease in the GABA-BD-receptor-ionophore complex activity led to a suppression of the immune response. The effect was achieved with: a blockade of the complex with bicuculline--a competitive inhibitor of the GABA-receptors: administration of a specific antagonist of the BD-receptors flumazenil or Ro 15-3505: or with blockade of chloride channels with picrotoxin. Activation of the GABA-ergic system causes an increase in bone marrow content of T-helper cells marked by L3T4. The immunomodulatory action of the GABA-ergic system is of central origin and can occur only when the hypothalamo-pituitary system is intact. Section of the pituitary stalk prevents accumulation of the T-helper cells in the bone marrow. The result show that the influence of GABA-ergic system on immunogenesis requires participation of both dopaminergic and serotoninergic systems.

Immunohistochemical study of the catecholaminergic innervation of the spinal cord of the rat using specific antibodies against dopamine and noradrenaline

We have assessed the relative contributions of dopaminergic and noradrenergic descending systems to the catecholaminergic innervation of the rat spinal cord. Fibres and terminals were labelled with their own neurotransmitter by using specific antibodies raised against dopamine (DA) and noradrenaline (NA) respectively. For this purpose, immunohistochemistry according to the peroxidase anti-peroxidase technique was performed in different experimental conditions. Two group of rats received intracisternal 6-hydroxy-dopamine (6-OHDA) injections either with or without benzatropine pretreatment. Animals of a third group were not pretreated at all. While 6-OHDA induced a complete disappearance of spinal NA-like immunoreactivity (NA-LI), except for scarce residual fibres in the thoracic intermedio-lateral cell column, DA-like immunoreactivity (DA-LI) was unaffected by the lesion. This strongly suggests that the antisera used specifically labelled NA-containing and DA-containing fibres respectively. Spinal DA-LI and NA-LI innervations differed markedly in their topographical distributions and in the morphology of the corresponding fibres. DA-LI innervation was restricted to laminae I, III and IV and to the intermediate zone, especially the autonomic areas. In the ventral horn, it was sparse and more visible after acidification of the fixation solution. NA-LI innervation was much more widely spread. In addition, the organization of NA-LI fibres suggests that the innervation of the whole dorsal horn comes from a group of fibres travelling, at least partially, in the superficial dorsal horn.

Biochemical resistance to development of morphine-dependence in rats: biogenic amines, its receptors and antibodies

The level of norepinephrine (NE), epinephrine (E) and dopamine (DA) in hypothalamus and blood plasma along with antibodies to NE, DA and serotonin (5-HT) and characteristics of alpha 1-, alpha 2-adrenergic, D2-dopaminergic and S2-serotoninergic receptors in synaptic brain membranes were studied in two groups of rats predisposed or resistant to the formation of physical morphine dependence. The resistant animals were characterized by a significant elevation of DA levels in blood plasma, elevation of antibodies to NE, and by higher concentration of alpha 2-adrenergic receptors in the brain cortex and of D2-receptors in striatum. The affinity of D2-receptors to dopamine in resistant rats also was higher than in predisposed animals. The other parameters studied did not differ significantly between the two groups. These findings suggest that the increased activity of DA and NE neurotransmitter systems can be a cause for the genetic resistance of some individuals among Wistar rats to the formation of physical dependence on morphine.

Habituation of an appetitive reflex in the honeybee

1. The proboscis extension reflex is an appetitive component of the bee's feeding behavior that is elicited by touching one antenna with a droplet of sugar water. Repetitive stimulation leads to a decrement and finally to the disappearance of the response, which can be restored by stimulating the contralateral antenna. This behavioral plasticity conforms to essential parametric characteristics for habituation. 2. The response was quantified by recording extracellularly from a muscle involved in proboscis movement, by measuring the duration of the proboscis extension, or by determining the number of trials necessary to abolish any visible response. 3. Because habituation was restricted to the repetitively stimulated antenna and did not generalize to the contralateral hemisphere, the neural circuits mediating habituation may be confined to one hemisphere. 4. State dependence of habituation could be demonstrated by showing that hungry animals exhibited a smaller response decrement and required more trials until disappearance of the response compared with satiated animals. The initial response and the subsequent response decrement are separate components determined by satiation level and stimulus strength. 5. Depleting the nervous system of monoamines by the use of reserpine abolished the reflex in 30% of the animals and reduced responsiveness in the remainder. Injection of octopamine or its metabolic precursor tyramine restored the reflex in reserpinized unresponsive animals, and tyramine also enhanced the muscle-spike discharge of reserpinized, responsive animals. In undepleted animals, tyramine application also accelerated the rate of habituation of the reflex. We therefore propose that octopaminergic neurons participate in mediating food arousal and the state dependence of habituation and, in a separate process, influence the response decrement during habituation. 6. Application of an acetylcholine esterase (AChE) inhibitor and a cholinergic receptor blocker confirmed histochemical data that implicate cholinergic transmission in the reflex pathways. 7. The combined pharmacological dissection of the reflex and immunocytochemical investigations of its chemical architecture provide evidence that the proboscis extension reflex is mediated by nonaminergic and monoaminergic pathways operating in parallel.

[Dopamine antibodies in the pathogenesis of parkinsonism]

L-DOPA and dopamine (DA) binding antibodies were found in the blood serum of Parkinsonian patients and middle-aged and elderly normal persons. DA-binding serum gamma-globulins of parkinsonian patients injected into rat caudate nuclei induced the pathogenetic mechanism of Parkinson's syndrome (generator of pathologically enhanced excitation) in these brain part and evoked main parkinsonian symptoms (oligokinesia, rigidity, tremor). The serum gamma-globulins of Parkinsonian patients without Da-antibodies caused less pronounced EEG disturbances. Parkinsonian symptoms developed rarely and were shorter and less pronounced compared with the DA-antibody effect. The DA binding antibodies role in Parkinson's syndrome pathogenesis and is L-DOPA therapeutic tolerance formation was discussed.

[Effects of passive administration of serotonin and catecholamine antibodies on alcohol consumption of C57Bl/6 mice in experimental alcoholism]

The experiments on C57Bl/6 mice with natural ethanol motivation have shown that passive injection of anti-noradrenaline and particularly antiserotonin antibodies reduces several times alcohol consumption by animals. On the contrary the injection of anti-dopamine antibodies to affect voluntary alcohol consumption by mice have been found.

Dopamine-immunoreactive neurones in the central nervous system of the pond snail Lymnaea stagnalis

The distribution of dopamine and dopamine-immunoreactive neurones was studied in the central nervous system of the snail Lymnaea stagnalis. The results from immunocytochemical labelling were compared with those from the application of the glyoxylic acid fluorescence method and 6-hydroxydopamine-induced pigment labelling. Comparisons were also made between the number of dopamine immunoreactive neurones and the dopamine content of the ganglia, measured by high-performance liquid chromatography. Dopamine immunocytochemistry proved to be superior to the other two histochemical techniques in terms of specificity and sensitivity. The 6-hydroxydopamine-induced pigment labelling failed to prove a useful tool for the in vivo identification of all dopamine-containing neurones. The distribution and number of dopamine-immunoreactive neurones and levels of biochemically measured dopamine in specific ganglia showed a close correspondence. By using the results of the dopamine immunocytochemistry and glyoxylic acid technique, a detailed map of dopamine-containing neurones was constructed. Dopamine-containing inter- and intra-ganglionic axon tracts were also demonstrated. The mapping of dopamine-containing neurones will facilitate further neurophysiological analysis of dopaminergic neural mechanisms in Lymnaea.

Localization of dopamine and its relation to the growth hormone producing cells in the central nervous system of the snail Lymnaea stagnalis

The distribution of dopamine in the central nervous system of the pond snail Lymnaea stagnalis was investigated by using immunocytochemistry and HPLC measurements. With both methods it was demonstrated that dopamine is predominantly present in the cerebral and pedal ganglia. The dopamine-immunoreactivity was mainly observed in nerve-fibers in the neuropile of the ganglia. Relatively few dopamine-immunopositive cell bodies (diameters 10-30 microns) were found. A large cell in the right pedal ganglion (the so-called RPeD1) stained positively with the dopamine antibody. It has previously been demonstrated that the growth hormone producing cells (GHCs) possess dopamine receptors on their cell bodies. However, dopamine-immunopositive fibers were observed only in the vicinity of the GHC nerve-endings and not close to the GHC cell bodies.

[Simultaneous detection of tryptamine and dopamine in the substantia nigra and raphe nuclei in rats using specific antibodies]

Using a double-labelling procedure, morphological relationships existing between dopaminergic and indoleaminergic neuronal systems in rat brain were investigated. Firstly, thanks to a tryptamine (T) antiserum, we visualized this indoleamine in all mesencephalic regions and showed that the T-immunoreactivity (IR) seems to overlap with the staining observed from serotonin (HT) and 5-methoxytryptamine (MT) antisera. Secondly, using a monoclonal anti-dopamine (DA) antibody and our anti-T antibodies, the simultaneous and specific detection of these compounds enabled us to define the chemically relationships existing between the dopaminergic and tryptaminergic neuronal systems from substantia nigra to raphe nuclei. No co-localization exists. But, the intensity of T-IR decreases from the back to the front, whereas the DA-staining decreases in the opposite way, indicating possible interactions at the end of substantia nigra and B9 area.